All images are astrometrically calibrated. For each of the 2116 mean fields, we provide the following:

  1. Instrumental: fields where the FITS data is in counts. These fields include the MAGZP header keyword, to convert instrument magnitudes to calibrated magnitudes.
  2. Photometrically Calibrated: photometrically calibrated fields, in that the FITS data is offsetted with the above-mentioned zero-point and converted to Janskies.
  3. Star-Removed: starless fields, where the FITS data was offsetted with the above-mentioned zero-point before star-removal processes were run and converted to Janskies.
  4. Individual Exposures: the individual exposures comprising the stack. The number of exposures ranges - background levels vary throughout the night, and we occassionaly exclude exposures with outlying backgrounds to enhance the quality of our mean-combined stack. With a future release version, each field will have exactly 12 quality-verified individual exposures.

Photometric Calibration

The instrumental images include the MAGZP keyword in their FITS headers. This represents the magnitude zero-point for each field image and can be used to calculate calibrated AB magnitudes, mag(MDW), from measured instrumental flux, as such:

mag(MDW) = -2.5*log10(measured flux [counts]) + MAGZP

The magnitude zero-point for each field is calculated by comparing the instrumental Hα magnitudes of sources in each field with the catalog-matched IGAPS' AB Hα magnitudes. We specifically try to offset our data such that the stellar locus of our color-color plots align with the IGAPS synthetic early-A reddening line.

For the photometrically calibrated and photometrically calibrated star-removed field images, we convert the MAGZP value into a physical flux zero-point and apply it to the FITS data unit. In this way, the measured values (e.g. in aperture photometry) result in a calibrated AB Hα magnitude. Note that the FITS data has the unit of Janskies.

mag(MDW) = -2.5*log10(measured flux [Jy] / 3631 [Jy])

Acknowledging MDW Data

Any publication using data from the MDW Sky Survey should include the following text:

Funding for the MDW Survey Project has been provided by the Michele and David Mittelman Family Foundation. David R. Mittelman, Dennis di Cicco, and Sean Walker are founding members of the survey and made possible the acquisition and reduction of the data. The Columbia University Astronomy Department is responsible for the final data reduction, calibration, and dissemination of the survey data.

Download Images

Note: as the initial release, some fields might have less files than others. These will be updated as we actively take extra exposures.